ttystikk
Well-Known Member
It's a great example of a shitty law.
CRI test and Mcree weighted results
- Thread starter Rahz
- Start date
verticalgrow
Well-Known Member
When
Rahz
Well-Known Member
I haven't gotten any updates but as far as I know it's going to happen over the next few months. It was free lamps for a grow test and since there were issues he still owes me a straight grow. He's wanting to put them all in a tent so he wasn't happy about the redo and I'm not going to bug him about it. He's a friend of mine that used to live near me so I know he will come through, just gotta be patient.
verticalgrow
Well-Known Member
ttystikk
Well-Known Member
What Kelvin temp?
My own experience with high CRI lighting (Philips 860W CDM, 93 CRI 3850K) taught me that high CRI is helpful but that Kelvin temp was still an important consideration.
ttystikk
Well-Known Member
I've been running a lot of 3500K and while it's been working well, I have also heard that 3000/90 is closer to what the plants really want. I have the need to buy some 20+ CXB3590 72V chips and I'm planning to buy them in 3000/90 in order to run a direct comparison.
Full disclosure; @Stephenj37826 was the first to mention it to me and your recent testing seems to confirm the hypothesis. All I need now is a spare $800!
verticalgrow
Well-Known Member
SSGrower
Well-Known Member
Have you seen 32Q, and 56Q, from cree? This is new to me but data sheet mentoins second generation of cxa, I thought that was the cxb.I would have expected 70>80>90 or 70<80<90
Interesting results 90>70>80
90 yielded the most and finished faster too
Thanks for sharing the CRI results. Good luck with next series of tests
Cree data sheet
Very expensive, high cri, cromacity region shifted from other cree chips (3200 vs 3000 or 3500, and 5600 vs. 5000 or 5700).
Any opinions? @Rahz , @welight (nifty litle bracket your showin in your avitar ther bud) @Stephenj37826
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Rahz
Well-Known Member
No strong opinions. High CRI does entail a shift to 630nm peak, but going from 90 to 95 might mean kicking the greens up a notch to provide the right color balance for the human eye. Anyway, would need to do a spectral analysis to see how the quantum output measures up, but at 110 LPW it's not looking like it's got anything on 90 CRI. Additionally, Cree had a press release recently on a CXB revision and it didn't seem much different than last years offering so I don't think these studio chips are going to make any waves.
SSGrower
Well-Known Member
Makse sense, I wondered why it wasn't tracking on here. Besides the fact they are 2x or more expensive than anything else, no significant increase in lumen output, just whatever efficacy would be added from a potential increse in ppf? Still would be nice to some numbers from you guys on them since you're the only resource I know of that compares these things across modeles and brands.
Rahz
Well-Known Member
Maybe
Depends on the phosphor efficiency.Would be interesting to see what would happen if the peak was moved from 630 to 650 on a typical 3000K/90CRI spectrum. I suspect the CRI would drop a bit. How that would affect the efficacy I'm not sure. QER would go up but how the phosphors would affect the efficiency I don't know. There's not a whole lot of difference in that regard from 80 to 90 CRI these days. Only a matter of time until there are agro cobs that are replacing street lights, but whether they will be tuned for our favorite plant is a different matter... but it seems likely that once the market is established we'll see a variety of options to cover various plant needs.
SSGrower
Well-Known Member
Seems you have the same questions I do. I'll sit back down on my couch and let you pros do what you do then....push the market please.....Maybe
Would be interesting to see what would happen if the peak was moved from 630 to 650 on a typical 3000K/90CRI spectrum. I suspect the CRI would drop a bit. How that would affect the efficacy I'm not sure. QER would go up but how the phosphors would affect the efficiency I don't know. There's not a whole lot of difference in that regard from 80 to 90 CRI these days. Only a matter of time until there are agro cobs that are replacing street lights, but whether they will be tuned for our favorite plant is a different matter... but it seems likely that once the market is established we'll see a variety of options to cover various plant needs.
rshackleferd
Well-Known Member
You can pull out charts etc and talk about what plants like and dont like. Ide rather the plants tell me what they like. Below is one of many test runs between 80 cri and 90 cri.
https://www.rollitup.org/t/one-more-run-with-the-cxbs-3000k-80-90-cri-qbs-are-next-in-line.938932/
https://www.rollitup.org/t/one-more-run-with-the-cxbs-3000k-80-90-cri-qbs-are-next-in-line.938932/
NoFucks2Give
Well-Known Member
Quantum yield (your average plant response) is RELATIVE to absorbed photons. It is NOT the action curve. It is NOT absolute.
The absorption curve shows very few photons are absorbed between 500nm and 600nm.
Of the few photons absorbed between 500 and 600nm, most of them are utilized in photosynthesis as shown in your average plant response curve. That is why when you see the absorption curve and action curve together they are nearly identical except for the slight drop in your average plant response curve.
For example at 480nm the absorption and action curves are at their greatest difference. Then notice how your average plant response curve is lowest at 480nm.
Notice how the absorption curve is below the action curve from 570 to 680nm. Then notice how the your average plant response curve raises to its peak between 570 and 680nm.
NoFucks2Give
Well-Known Member
@Malocan makes a very valid point.
Citizen's PPF/Watt numbers look correct. The numbers generated by Alesh's SPD spreadsheet look very high.
The attached NIST document points out that the measurement distance is SIGNIFICANT.
CIE 127 specifies two distances to be used; 100 mm and 316 mm, and a source point and uses the Inverse Square Law to resolve
@wietefras the self proclaimed expert on the subject of LED measurements in this thread falls short in his understanding of LED measurements.
IOn this post in another thread @wietefras said:
From the following two images it is clear that distance and Inverse Square Law is very relevant in this situation.
The SPD spreadsheet in the "Math behind" thread also does not take distance into consideration. The SPD graph in an LED datasheet is normalized and therefore has no real world amplitude. The SPD shows the relative radiometric power distribution but there is no value associated with the high peak's amplitude.
What I have seen some do here is use the lm/W value and apply it to the radiometric characteristics of test current, test forward voltage, and SPD.
The SPD values are normalized radiometric values and lm/W is luminous applicable only to to human vision perception and CANNOT be used with the radiometric values that do not have any relationship with luminous values.
If it were true (it is not) that distance did not matter then the SPD spreadsheet numbers would have some significance.
This misconception being spread around on this site that distance does not matter may explain why the grow light fixtures are hung so far from the canopy in most of the pictures I have seen on this site.
The key to an efficient grow fixture is to have good uniformity that will allow the fixture to be located closer to the canopy increasing flux intensity exponentially as the distance decreases.
FROM THE ATTACHED NIST DOCUMENT PAGE 3
The Averaged LED (Luminous/Radiant) Intensity Is defined by CIE with the geometry shown in Fig. 1. This quantity is recommended for individual LEDs having a lens optic (such as a 5 mm epoxy type). Such LEDs do not behave as a point source, and measured luminous intensity values tend to vary significantly with the measurement distance and photometer aperture size. This standardized geometry will avoid such measurement variations and enable accurate comparison of measured values. The normal luminous intensity may be used for other LEDs measured as a point source (with a sufficiently large distance).
FIG 1 FROM PAGE 2
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Stephenj37826
Well-Known Member
It is in my opinion that the 3000k 90 has a very favorable r/fr ratio. It is in my opinion that at a 60 nm split 6:1-8:1 is r/fr is optimum. It's not specific to wavelength necessarily but rather a wide range. The Emerson effect isn't specific to certain wavelengths like many people think. In my opinion 630/690 ratio it's as important as 660/720...... So on so forth.